(NaturalNews) Contamination of water supplies and illegal use of veterinary drugs has led to the severe contamination of Chinese fish farms, with potentially serious health consequences for those who eat the fish.

China produces 70 percent of the world's farmed fish, and since the 1980s has become the biggest seafood exporter in the world. Yet this growth has only exacerbated the pollution problems already facing China's water sources. The high density of fish farms in regions like the Fuqing Province in the south has led to the discharge of huge quantities of wastewater into already compromised rivers.

"Our waters here are filthy," said Ye Chao, an eel and shrimp farmer from Fuqing. "There are simply too many aquaculture farms in this area. They're all discharging water here, fouling up other farms."

The Chinese government has declared more than half of the rivers in the country too polluted to drink from. Many sections of Fuqing's major waterway, the Long River, have been declared too toxic for any use.

Pollution of river and coastal waters comes from rapidly growing industries that are discharging pesticides, oil, mercury, lead, copper and agricultural runoff. This pollution has caused massive die-offs at fish farms, leading farmers to illegally mix veterinary drugs into their ponds to try and keep their fish alive. According to farmers who eventually abandoned such practices, not using drugs led to an immediate 30 percent increase in fish mortality.

Beyond the health risks to the fish themselves, pollution causes the accumulation of toxic substances in the bodies of the fish, which poses a health risk to people who eat them.

Wang Wu, a professor from the Shanghai Fisheries University, attributes the problem to unbridled growth. "For 50 years, we've blindly emphasized economic growth," he said. "The only pursuit has been GDP, and now we can see that the water turns dirty and the seafood gets dangerous."